JP2020031961A - Radiographic system - Google Patents

Abstract

To inhibit the occurrence of an artifact due to offset correction when a plurality of radiographic images each with a different binning number are acquired.SOLUTION: Control means 22 of a radiography apparatus 1, when a plurality of radiographic images each with a different binning number are captured in succession, matches the binning number at the time of reset before image acquisition with the binning number at the time of image acquisition and acquires a plurality of offset images respectively corresponding to the plurality of radiographic images, to thereby apply offset correction processing to the radiographic images.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a radiographic imaging system.

  Various radiation image capturing devices have been developed that include a radiation detector (FPD: (Flat Panel Detector)) that generates charges in a radiation detecting element according to the dose of irradiated radiation and reads out the generated charges as image data. I have.

  In such a radiation image capturing apparatus, even in a state where radiation is not irradiated, dark charge is generated in each radiation detection element due to thermal excitation or the like by heat of the radiation detection element, and this electric charge is accumulated in the radiation detection element. Includes offset due to dark charge. Therefore, in order to acquire a high-quality radiation image, usually, an offset image acquisition process of reading data of an offset due to dark charge (hereinafter, referred to as an “offset image”) from each radiation detection element without irradiating radiation, This is performed before or after a radiation image acquisition process of acquiring a radiation image by accumulating and reading out charges generated by irradiation of radiation in each radiation detection element. Then, by subtracting the offset image from the radiation image acquired by the radiation image acquisition processing, offset correction for removing the offset due to dark charge from the radiation image is performed.

  By the way, when the radiation subtraction is performed by continuously irradiating the subject with radiation having different energy distributions and acquiring a plurality of radiation images using the above-described radiation image capturing apparatus, the energy subtraction processing is performed. You need to get

  For example, Patent Literature 1 discloses that a radiation detector is irradiated at a first X-ray energy level over time t1 and read by the radiation detector to obtain a first irradiation reading value, and a second radiation reading is acquired over time t2. Irradiating the radiation detector at the X-ray energy level of and reading the radiation detector to obtain a second irradiation reading, and after reset, corresponding to the first irradiation reading after a time equal to t1. A radiation detector reading is taken to obtain a first offset reading, and after a time equal to t2, a radiation detector reading is taken to obtain a second offset reading corresponding to the second irradiation reading. It is described.

JP-T-2004-516874

  In the energy subtraction process, in order to obtain a high-definition image while suppressing the image capacity and the processing time, in the radiation image capturing apparatus, reading out the charge accumulated in the imaging by irradiating the subject with radiation at a low tube voltage, It is conceivable that the reading is performed with a larger binning number than the reading of the electric charge accumulated in the imaging in which the subject is irradiated with radiation at a high tube voltage.

  However, the technique described in Patent Literature 1 does not consider the acquisition of an offset image when a plurality of radiation images are successively acquired with different binning numbers, and an artifact is generated in the offset-corrected radiation image. There was a possibility that it would occur.

  An object of the present invention is to suppress the occurrence of artifacts due to offset correction when a plurality of radiation images are acquired with different binning numbers.

In order to solve the above problems, the invention described in claim 1 is:
A plurality of radiation detecting elements arranged two-dimensionally,
An image acquisition circuit for acquiring and acquiring an image by causing the radiation detection element to accumulate and emit charges and reading out the emitted charges.
A radiographic imaging system comprising:
By controlling the image acquisition circuit, a radiation image acquisition unit that continuously acquires a plurality of radiation images by varying at least the number of binning,
By controlling the image acquisition circuit, the number of binning at the time of resetting the radiation detection element before image acquisition and the number of binning at the time of image acquisition coincide with those at the time of acquisition of the series of the plurality of radiation images, and Offset image acquisition means for acquiring the plurality of offset images corresponding to each of the radiation images,
Correction means for performing offset correction on the plurality of radiation images using the offset images corresponding to each of the plurality of radiation images,
Is provided.

The invention according to claim 2 is the invention according to claim 1,
The offset image acquiring unit may further match the charge accumulation time of the radiation detecting element with that at the time of acquisition of each of the series of the plurality of radiation images, so that the plurality of offsets corresponding to each of the plurality of radiation images are obtained. Get an image.

The invention according to claim 3 is the invention according to claim 1 or 2,
The image acquisition circuit includes a switch unit that emits electric charge from the radiation detection element when turned on.
The offset image acquisition unit may further include at least one of a reset scan cycle, an on-time of the switch unit in the reset scan cycle, a read scan cycle, and an on-time of the switch unit in the read scan cycle. The plurality of offset images corresponding to each of the plurality of radiation images are acquired in agreement with those at the time of acquiring the plurality of radiation images.

The invention according to claim 4 is the invention according to any one of claims 1 to 3,
A radiation irradiation device that irradiates the radiation detection element with radiation at different tube voltages a plurality of times,
The radiation image acquisition unit acquires the plurality of radiation images using radiation irradiated at different tube voltages.

The invention according to claim 5 is the invention according to claim 4,
The radiation image acquisition unit controls the image acquisition circuit, and reads out the radiographing performed by the radiation irradiated at the low tube voltage among the radiations irradiated at the different tube voltages, using the radiation irradiated at the high tube voltage. Is performed with a larger number of binnings than the reading in the photographing.

  According to the present invention, it is possible to suppress the occurrence of artifacts due to offset correction when a plurality of radiographic images are acquired with different binning numbers.

It is a figure showing the whole radiation image photography system composition concerning this embodiment. FIG. 2 is a perspective view illustrating the radiation image capturing apparatus according to the embodiment. It is sectional drawing which follows the XX line in FIG. FIG. 2 is a plan view illustrating a configuration of a substrate of the radiation image capturing apparatus. FIG. 5 is an enlarged view illustrating a configuration of a radiation detection element, a TFT, and the like formed in a small area on the substrate in FIG. 4. It is a block diagram showing the equivalent circuit of a radiographic imaging device. It is a block diagram showing the equivalent circuit about one pixel which comprises a detection part. FIG. 4 is a diagram schematically illustrating an image acquisition sequence in the radiation image capturing apparatus 1 after an imaging start instruction according to the first embodiment. FIG. 11 is a diagram schematically illustrating an image acquisition sequence in the radiation image capturing apparatus 1 after an imaging start instruction according to the second embodiment. (A) is a diagram schematically showing a subject signal and a lag in the first image, the second image, and the first offset image in the second embodiment, and (b) is a diagram in which the first offset image is subtracted from the first image. FIG. 4 is a diagram schematically showing a corrected first image. In the case where the reset is continued before the offset image is obtained, the elapsed time t from the time when the second image is obtained and the magnification α of the lag generated in the offset image (a value indicating how many times the lag remains in the second image) FIG.

  Hereinafter, embodiments of a radiation image capturing system and a radiation image capturing apparatus according to the present invention will be described with reference to the drawings.

  In the following, a case where the radiographic image capturing apparatus is a so-called indirect type radiographic image capturing apparatus that includes a scintillator or the like and converts the irradiated radiation into electromagnetic waves of another wavelength such as visible light to obtain an electric signal. As will be described, the present invention is also applicable to a direct type radiographic imaging apparatus. Further, a case where the radiation image capturing apparatus is a portable type will be described, but the present invention is also applied to a radiation image capturing apparatus formed integrally with a support base or the like.

[Radiation imaging system]
FIG. 1 is a diagram illustrating an overall configuration of a radiation image capturing system 50 according to the present embodiment.
For example, as shown in FIG. 1, the radiographic image capturing system 50 radiates radiation to capture an image of a subject (part of a patient's body (not shown) (part to be imaged of the patient)), Adjacent to the room R1, a front room R2 in which an operator (user) such as a radiologist performs various operations such as control of the start of irradiation of a subject with radiation, and the outside thereof.

  Specifically, as shown in FIG. 1, the radiographic image capturing system 50 performs image processing on the radiographic image capturing apparatus 1 that performs a radiographic image obtaining process and the image data of the radiographic image obtained by the radiographic image capturing apparatus 1. A console 58 for performing processing and the like, a radiation generator 55 for irradiating the radiation image capturing apparatus 1 with radiation, and the like are provided.

  The imaging room R1 includes, for example, a bucky device 51 that can be loaded with the radiation image capturing device 1, a radiation source 52 having an X-ray tube (not shown) that generates radiation for irradiating a subject, and radiation that controls the radiation source 52. A radiation irradiating device having a generator 55 and a relay 54 having a wireless antenna 53 and relaying communication between the radiation image capturing device 1 and another device such as a console 58 or a radiation generator 55 are provided. I have.

In FIG. 1, when the portable radiation image capturing apparatus 1 is used by being loaded into the cassette holding unit 51 a of the bucky apparatus 51, and when the portable radiation image capturing apparatus 1 is used alone without being loaded into the bucky apparatus 51, In this case, the patient is placed on the upper surface of a bucky device 51B for position photographing, and the patient's hand or the like as a subject is placed on the radiation incident surface R (see FIG. 2). The image photographing apparatus 1 may be formed integrally with the bucky device 51, the support base, and the like.
Here, when the portable radiographic image capturing apparatus 1 is used alone without being loaded into the bucky apparatus 51, it is disposed on the upper surface side of the bucky apparatus 51B for recumbent radiography and its radiation incident surface R (see FIG. 2). In addition to placing and using a patient's hand or the like as a subject on the upper side, for example, it is arranged on the upper surface side of a bed or the like provided in the radiographing room R1 and placed on the radiation incident surface R (see FIG. 2). It is also possible to place the hand or the like of a certain patient, or to insert it between the bed and the waist or feet of a patient lying on a bed, for example.

  The repeater 54 is connected to the console 58 and the radiation generator 55 by a wired (LAN) cable or the like, and transmits information to the repeater 54 between the radiation image capturing apparatus 1 and the console 58. In this case, a converter (not shown) for converting a signal for LAN communication or the like into a signal for transmitting information to / from the radiation generating device 55 and performing the reverse conversion is also provided.

  In addition, the repeater 54 is connected to the bucky device 51 by wire, and performs communication between the radiographic image capturing device 1 loaded in the bucky device 51 and other devices such as the console 58 and the radiation generating device 55. The configuration is such that the communication can be performed in a wired manner via the repeater 54.

In FIG. 1, the radiographic image capturing apparatus 1, specifically, the radiographic image capturing apparatus 1 that is not mounted on the bucky device 51 and the repeater 54 are wirelessly connected, and the radiographic image capturing apparatus 1 and the console 58 and the radiation Although a case is shown in which communication with another device such as the generator 55 can be performed in a wireless manner via the repeater 54, the radiation image capturing apparatus 1 and the repeater 54 Can be connected in a wired manner, and communication between the radiation image capturing apparatus 1 and another apparatus can be performed in a wired manner via the repeater 54.
Note that the radiographic image capturing apparatus 1 can be configured to be able to be wirelessly connected to the repeater 54 even when the radiographic image capturing apparatus 1 is loaded in the bucky device 51.

FIG. 1 shows a case where, as the bucky device 51, one bucky device 51A for upright imaging and one bucky device 51B for recumbent imaging are provided in the imaging room R1. The number and types of the bucky devices 51 provided in the photographing room R1 are not particularly limited.
FIG. 1 shows a case where, as the radiation source 52, one radiation source 52A associated with the Bucky device 51 and one portable radiation source 52B are provided in the imaging room R1. However, the number and types of the radiation sources 52 provided in the imaging room R1 are not particularly limited.

[Radiation generator]
The imaging room R1 is provided with a radiation generation device 55 that controls irradiation of radiation from the radiation source 52 to the radiation image capturing device 1.
In the present embodiment, a console 57 for the radiation generator 55 is provided in the front room R2 adjacent to the imaging room R1, and a user such as a radiologist is provided on the console 57 for the radiation generator 55. An exposure switch 56 is provided for operating when instructing start of radiation irradiation or the like.

The exposure switch 56 includes a two-stage switch of a first switch and a second switch.
When the first switch is pressed, the exposure switch 56 is configured to transmit an activation signal to the radiation generator 55 via the console 57.
Then, upon receiving this activation signal, the radiation generator 55 is configured to start the rotation of the anode of the X-ray tube of the radiation source 52, thereby bringing the radiation source 52 into a standby state. Further, the relay switch 54 is configured to transmit a notification signal of pressing the first switch to the radiation image capturing apparatus 1.

  Further, when the second switch is pressed, the exposure switch 56 is configured to transmit a radiation irradiation start signal to the radiation generator 55 via the console 57.

  Upon receiving the radiation irradiation start signal from the exposure switch 56, the radiation generator 55 is configured to transmit a notification signal of pressing the second switch to the radiation image capturing apparatus 1 via the relay 54. When the radiographic image capturing apparatus 1 receives the press notification signal of the second switch and is ready to complete an offset image acquisition process described later, the radiographic image capturing apparatus 1 transmits an interlock release signal to the radiation generating apparatus 55 via the repeater 54. Send. The radiation generator 55 is configured to irradiate radiation from the X-ray tube of the radiation source 52 when receiving the interlock release signal transmitted from the radiation image capturing apparatus 1 via the relay 54.

  The radiation generator 55 can irradiate radiation from the radiation source 52 a plurality of times with different tube voltages in response to receiving a radiation irradiation start signal from the exposure switch 56 and an interlock release signal from the radiation image capturing device 1. It is possible. In the present embodiment, when a DES (Dual Energy Subtraction) mode (details will be described later) is set as the imaging mode, the radiation generation device 55 transmits the radiation irradiation start signal from the exposure switch 56 and the radiation image capturing device 1. Irradiates the radiation from the radiation source 52 a plurality of times at different tube voltages in response to the reception of the interlock release signal.

  In addition, the radiation generator 55 adjusts the position and the radiation irradiation direction of the radiation source 52 such that the user operates the console 57, for example, so that the radiation image capturing apparatus 1 is appropriately irradiated with the radiation. Various adjustments such as adjusting the aperture of the radiation source 52 so that the radiation is irradiated into a predetermined area of the radiation image capturing apparatus 1, adjusting the radiation source 52 so that an appropriate dose of radiation is emitted, and the like. Is performed on the radiation source 52. In addition, you may comprise so that a user may perform these processes manually.

[console]
For example, as shown in FIG. 1, the console 58 includes a display unit 58a such as a CRT (Cathode Ray Tube) or an LCD (Liquid Crystal Display), a storage unit 59 such as an HDD (Hard Disk Drive), and a console 58. A communication unit 58c connected to the repeater 54 via a LAN cable or the like to communicate with another device such as the radiation image capturing apparatus 1, a keyboard 58, This is a computer including an input unit 60 such as a mouse.

Although FIG. 1 shows a case where the console 58 is provided outside the photographing room R1 and the front room R2, the console 58 may be provided in the front room R2, for example.
Although FIG. 1 shows a case where the storage unit 59 is connected to the console 58, the storage unit 59 may be built in the console 58.

When the communication unit 58c receives the image data of the radiation image captured by the radiation image capturing apparatus 1 from the radiation image capturing apparatus 1 via the repeater 54, the control unit 58b of the console 58 performs a decompression process on the image data. And a predetermined image processing such as automatic gradation processing is performed to create a diagnostic radiation image.
The control unit 58b of the console 58 displays the diagnostic radiation image on the display unit 58a or communicates the image data of the diagnostic radiation image according to an instruction from the input unit 60 or the like operated by the user. The data is output from the unit 58c or the like and transmitted to another device (not shown) such as an imager or a data management server.

  In the present embodiment, a description will be given assuming that the radiation image capturing apparatus 1 performs correction processing such as offset correction processing and gain correction processing. To the console 58, and the console 58 may perform a correction process such as an offset correction process or a gain correction process.

[Radiation imaging system]
FIG. 2 is an external perspective view of the radiation image capturing apparatus according to the present embodiment, and FIG. 3 is a cross-sectional view taken along line XX of FIG.
As shown in FIGS. 2 and 3, the radiation image capturing apparatus 1 according to the present embodiment is configured as a portable (cassette type) apparatus in which a scintillator 3, a substrate 4, and the like are stored in a housing 2. .

The casing 2 has at least a surface R on the side that receives radiation (hereinafter referred to as a “radiation incident surface R”) made of a material such as a carbon plate or plastic that transmits radiation.
2 and 3, the case 2 is a so-called lunch box type formed by a frame plate 2A and a back plate 2B. It is also possible to form a so-called monocoque type.

  As shown in FIG. 2, in the present embodiment, a power switch 36, an indicator 37 composed of an LED or the like, and a battery 41 (see FIG. 6 described later) are exchanged on the side surface of the housing 2. A lid member 38 and the like which can be opened and closed are disposed. In the present embodiment, an antenna 39 a is embedded in the side surface of the lid member 38.

  As shown in FIG. 3, a base 31 is disposed inside the housing 2 via a lead thin plate or the like (not shown) below the substrate 4, and electronic components 32 and the like are provided on the base 31. The mounted PCB board 33, buffer member 34, and the like are attached. In this embodiment, a glass substrate 35 for protecting the substrate 4 and the scintillator 3 is provided on the radiation incident surface R side of the scintillator 3.

  The scintillator 3 is arranged so as to face a detection unit P of the substrate 4 described later. The scintillator 3 is, for example, one that has a phosphor as a main component, and that upon receiving radiation, converts it into an electromagnetic wave having a wavelength of 300 to 800 nm, that is, an electromagnetic wave centered on visible light and outputs it.

  In the present embodiment, the substrate 4 is formed of a glass substrate. As shown in FIG. 4, a plurality of scanning lines 5 and a plurality of signal lines are provided on a surface 4 a of the substrate 4 on the side facing the scintillator 3. 6 are arranged so as to cross each other. A radiation detecting element 7 is provided in each region r partitioned by the plurality of scanning lines 5 and the plurality of signal lines 6 on the surface 4a of the substrate 4.

  As described above, the entire region r in which the plurality of radiation detection elements 7 arranged two-dimensionally in each region r partitioned by the scanning lines 5 and the signal lines 6 is shown, that is, shown by a dashed line in FIG. The region is defined as a detection unit P.

In the present embodiment, a photodiode is used as the radiation detection element 7, but for example, a phototransistor or the like can also be used.
Each of the radiation detecting elements 7 is connected to a source electrode 8s of a TFT 8 which is a switching means, as shown in FIG. 4 or FIG. 5 which is an enlarged view of FIG. The drain electrode 8 d of the TFT 8 is connected to the signal line 6.

The TFT 8 is turned on when a turn-on voltage is applied to the connected scan line 5 by a scan driving unit 15 described later, and when a turn-on voltage is applied to the gate electrode 8g via the scan line 5, the TFT 8 is turned on. The electric charges accumulated in 7 are emitted from the radiation detecting element 7 to the signal line 6.
The TFT 8 is turned off when an off-voltage is applied to the connected scanning line 5 and an off-voltage is applied to the gate electrode 8 g via the scanning line 5, and the charge from the radiation detecting element 7 to the signal line 6 is changed. Is stopped, and the charge generated in the radiation detecting element 7 is held and accumulated in the radiation detecting element 7.

  Here, the circuit configuration of the radiation image capturing apparatus 1 will be described. FIG. 6 is a block diagram illustrating an equivalent circuit of the radiation image capturing apparatus 1 according to the present embodiment, and FIG. 7 is a block diagram illustrating an equivalent circuit for one pixel included in the detection unit P.

In each radiation detecting element 7 of the detecting section P of the substrate 4, a bias line 9 is connected to the second electrode 78, and each bias line 9 is connected to a connection 10 and connected to a bias power supply 14. The bias power supply 14 applies a bias voltage to the second electrode 78 of each radiation detection element 7 via the connection 10 and each bias line 9.
Further, the bias power supply 14 is connected to control means 22 described later, and the control means 22 controls a bias voltage applied from the bias power supply 14 to each radiation detection element 7.

  In the present embodiment, the bias power source 14 supplies a bias voltage to the second electrode 78 of the radiation detection element 7 via the bias line 9 as a bias voltage equal to or lower than a voltage applied to the first electrode 74 of the radiation detection element 7 (that is, a so-called voltage). Reverse bias voltage) is applied.

  The first electrode 74 of each radiation detection element 7 is connected to the source electrode 8s (denoted by S in FIGS. 6 and 7) of the TFT 8, and the gate electrode 8g of each TFT 8 (FIGS. 6 and 7). In the drawing, G is connected to each of the lines L1 to Lx of the scanning line 5 extending from the gate driver 15b of the scanning driving unit 15 described later. A drain electrode 8 d (denoted by D in FIGS. 6 and 7) of each TFT 8 is connected to each signal line 6.

  The scanning driving unit 15 includes a power supply circuit 15a that supplies an on-voltage and an off-voltage to the gate driver 15b via the wiring 15c and a voltage applied to each of the lines L1 to Lx of the scanning line 5 between the on-voltage and the off-voltage. And a gate driver 15b for switching each TFT 8 between the on state and the off state.

  As shown in FIGS. 6 and 7, each signal line 6 is connected to each read circuit 17 formed in the read IC 16. In this embodiment, the readout IC 16 is provided with one readout circuit 17 for each signal line 6.

  The readout circuit 17 includes an amplifier circuit 18, a correlated double sampling circuit 19, and the like. The reading IC 16 further includes an analog multiplexer 21 and an A / D converter 20. In FIGS. 6 and 7, the correlated double sampling circuit 19 is described as CDS. In FIG. 7, the analog multiplexer 21 is omitted.

  In the present embodiment, the amplifier circuit 18 is configured by a charge amplifier circuit, and includes an operational amplifier 18a, a capacitor 18b connected in parallel to the operational amplifier 18a, and a charge reset switch 18c. Further, a power supply unit 18d for supplying power to the amplifier circuit 18 is connected to the amplifier circuit 18.

The signal line 6 is connected to the inverting input terminal on the input side of the operational amplifier 18 a of the amplifier circuit 18, and the reference potential V ₀ is applied to the non-inverting input terminal on the input side of the amplifier circuit 18. . Note that the reference potential V ₀ is set to an appropriate value, and in the present embodiment, for example, 0 [V] is applied.

Further, the charge reset switch 18c of the amplifier circuit 18 is connected to the control means 22, and the control means 22 controls on / off.
When the charge reset switch 18c is off and the TFT 8 is turned on (ie, when an on-voltage is applied to the gate electrode 8g of the TFT 8 via the scanning line 5), each of the TFTs 8 turned on is turned on. The electric charge accumulated from each radiation detection element 7 is released to the signal line 6 via the signal line 6, and the electric charge flows through the signal line 6, flows into the capacitor 18b of the amplifier circuit 18, and is accumulated.

  In the amplifier circuit 18, a voltage value corresponding to the amount of charge stored in the capacitor 18b is output from the output side of the operational amplifier 18a. The amplification circuit 18 outputs a voltage value in accordance with the amount of charge output from each radiation detection element 7 and performs charge-voltage conversion in this manner.

When resetting the amplifier circuit 18, when the charge reset switch 18c is turned on, the input side and the output side of the amplifier circuit 18 are short-circuited, and the electric charge accumulated in the capacitor 18b is discharged. Then, the discharged circuit passes through the inside of the operational amplifier 18a from the output terminal side of the operational amplifier 18a, exits from the non-inverting input terminal, is grounded, or flows out to the power supply unit 18d, so that the amplifier circuit 18 is reset. It has become.
Note that the amplification circuit 18 may be configured to output a current according to the charge output from the radiation detection element 7.

The output side of the amplifier circuit 18 is connected to a correlated double sampling (CDS) circuit 19. The correlated double sampling circuit 19 outputs the output voltage of the amplifier circuit 18 before applying the on-voltage to the scanning line 5 to which the radiation detection element 7 from which the signal is to be read is connected (while the off-voltage is being applied). After sampling and holding, an ON voltage is applied to the corresponding scanning line 5 to read out signal charges of the radiation detecting element 7, and a difference between output voltages of the amplifier circuit 18 after applying an OFF voltage to the corresponding scanning line 5 is output. It has become.
Note that the output voltage of the amplifier circuit 18 after reading out the signal charge may be sampled and held to make a difference.

  The control means 22 controls the amplifying circuit 18 and the correlated double sampling circuit 19 in the process of reading out image data from each radiation detecting element 7 so that the electric charge released from each radiation detecting element 7 is amplified by the amplifying circuit. The charge-voltage conversion is performed at 18, and the voltage value obtained by the charge-voltage conversion is sampled by the correlated double sampling circuit 19 and output as image data to the downstream side.

  The image data of each radiation detection element 7 output from the correlated double sampling circuit 19 is transmitted to the analog multiplexer 21, and is sequentially transmitted from the analog multiplexer 21 to the A / D converter 20. The image data is sequentially converted into digital value image data by the A / D converter 20, output to the storage means 40, and sequentially stored.

  As described above, in the radiation image capturing apparatus 1, the charge is accumulated in the radiation detection element 7 by the image acquisition circuit including the scan driving unit 15 and the readout circuit 17, and the accumulated charge is transmitted from the radiation detection element 7. By emitting and reading, an image can be obtained.

  The control means 22 sequentially switches each of the lines L1 to Lx of the scanning line 5 to which the ON voltage is applied from the gate driver 15b of the scanning driving means 15 as described later, and each time the switching is performed, the above-described radiation detection is performed. Control is performed so as to perform a process of reading image data from the element 7.

The control means 22 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a computer in which an input / output interface and the like are connected to a bus, an FPGA (Field Programmable Gate Array), etc. It is configured. It may be constituted by a dedicated control circuit. The control means 22 controls the operation of each member of the radiation image capturing apparatus 1 and the like.
Also, as shown in FIG. 6 and the like, the storage unit 40 including a DRAM (Dynamic RAM) or the like is connected to the control unit 22.

Further, in the present embodiment, the communication unit 39 is connected to the control unit 22. The communication unit 39 transmits and receives data and signals to and from the outside via a wireless system or a wired system via an antenna 39a and a connector 39b.
Further, in the present embodiment, a battery 41 for supplying power to each functional unit such as the detecting unit P, the scanning drive unit 15, the readout circuit 17, the storage unit 40, and the bias power supply 14 is connected to the control unit 22. Have been. When the battery 41 is charged by supplying power to the battery 41 from a charging device (not shown), a connection terminal 42 for connecting the charging device to the battery 41 is attached to the battery 41.

  The control unit 22 controls the bias power supply 14 to set a bias voltage to be applied from the bias power supply 14 to each radiation detecting element 7 and controls on / off of the charge reset switch 18 c of the amplification circuit 18 of the readout circuit 17. The operation of each functional unit of the radiation image capturing apparatus 1 is controlled, for example, by transmitting a pulse signal to the correlated double sampling circuit 19 to control ON / OFF of the sample hold function. .

<Operation of radiation imaging system>
Hereinafter, the operation of the radiation image capturing system 50 will be described.
In the present embodiment, a first image is obtained by irradiating radiation at a first tube voltage, and then a second image is obtained by irradiating radiation at a second tube voltage (first tube voltage <second tube voltage). Then, in a mode in which a difference image is generated using the first image and the second image (referred to as a DES mode), an offset image (first offset image) corresponding to each image is obtained before the first image and the second image are obtained. , A second offset image) will be described.

  First, the photographer performs photographing preparation. For example, a photographing menu (for example, a photographing mode (here, a DES mode), a photographing region, a photographing direction, and the like) is selected via the input unit 60 on the console 58, and a photographing start instruction is input. The photographer performs positioning of the subject, the radiation source 52, and the radiation image capturing apparatus 1.

In the console 58, when a photographing menu is selected by the input unit 60 and a photographing start instruction is input, the control unit 58b transmits a photographing start instruction in the selected photographing menu by the communication unit 58c to the radiation generator 55 and the radiation source. The image is transmitted to the image photographing device 1. Upon receiving the radiographing menu, the radiation generator 55 emits radiation (e.g., radiation (first radiation) for acquiring a first image) and radiation (second radiation) for acquiring a second image according to the radiation menu. (Irradiation), tube current, tube voltage, irradiation time, radiation irradiation interval between the first irradiation and the second irradiation, and the like.
When the control unit 22 of the radiographic image capturing apparatus 1 receives the radiographic menu, the control unit 22 obtains radiographic image acquisition conditions (for example, image acquisition conditions of the first image (charge accumulation time (accumulation time) Ti1, number of binning, readout). The scanning period Tr1, the on-time Ton1 of the TFT 8 in the readout scanning period), the image acquisition conditions of the second image (the accumulation time Ti2, the number of binning, the readout scanning period Tr2, the on-time Ton2 of the TFT8 in the readout scanning period), Reset conditions of the radiation detection element 7 (number of binning, reset scan cycle, ON time of the TFT 8 in the reset scan cycle), and offset image acquisition conditions (for example, image acquisition conditions of the first offset image (accumulation time, binning number, readout) Scanning period, on-time of the TFT 8 in the reading scanning period), Image acquisition conditions of the offset image (accumulation time, number of binning, readout scan cycle, on-time of TFT 8 in readout scan cycle), reset condition of radiation detection element 7 before image acquisition (number of binnings, reset scan cycle, reset scan cycle The ON time of the TFT 8) is read out from the storage means 40 and set.

  Here, “reset” refers to releasing extra charges such as dark charges accumulated in each radiation detecting element 7 before accumulating the charges in each radiation detecting element 7 for image acquisition. .

Further, the binning number indicates the number of pixels to be collected as one pixel. For example, binning in the vertical direction (extending direction of the signal lines 6; the same applies hereinafter) can be realized by simultaneously turning on the gate electrodes 8g of a plurality of lines of the adjacent scanning lines 5 (analog binning). Binning in the horizontal direction (the extending direction of the scanning line 5; the same applies hereinafter) can be realized by adding or averaging the values of a plurality of pixels adjacent in the horizontal direction of the image data (digital binning). In the present embodiment, the number of vertical binning when acquiring the first image> the number of vertical binning when acquiring the second image. By increasing the number of bins in the vertical direction at the time of acquiring the first image, high-speed reading of the first image becomes possible, so that the shooting interval between the first image and the second image can be reduced, and the body of the subject can be shortened. It is possible to suppress an artifact of a captured image due to motion.
In the present embodiment, the number of vertical binning times × the number of horizontal binning at the time of acquiring the first image is 2 × 1, the number of vertical binning times × the number of horizontal binning at the time of acquiring the second image, and the reset before the image acquisition. The case where the number of binning in the vertical direction × the number of binning in the horizontal direction at the time is set to 1 × 1 will be described as an example. In the following description, the number of binnings is represented by the number of vertical binning times the number of horizontal binning. For example, the binning number (2 × 1) indicates that the vertical binning number is 2 and the horizontal binning number is 1.

  Further, the read-out scanning cycle refers to a time for reading out electric charges from each radiation detecting element 7 and obtaining image data, and is substantially equal to an on-time of the TFT 8 + a processing time of the correlated double sampling circuit 19. The reset scanning cycle refers to a time for discharging (reading out) charges from each radiation detecting element 7 and is substantially equal to an ON time of the TFT 8. Since the processing time of the correlated double sampling circuit 19 is not required for the reset scanning cycle, the reset scanning cycle can be shortened with respect to the read scanning cycle. Note that the read scan can be used instead of the reset scan. In this case, the reset scan cycle is equivalent to the read scan cycle, but the number of types of scan sequences is reduced, so that the design can be simplified. It is desirable to use which advantage is prioritized depending on the design policy.

  In the present embodiment, the binning number at the time of acquiring the first offset image is set to match the binning number at the time of acquiring the first image, and the binning number at the time of acquiring the second offset image is the binning number at the time of acquiring the second image. The one that matches the number is set. The number of bins at the time of resetting the radiation detection element 7 before acquiring a series of offset images is set to be the same as the number of binning at the time of resetting the radiation detection element 7 before acquiring a series of radiation images. If the number of bins at the time of reset before image acquisition and the number of binning at the time of image acquisition are different between when acquiring a radiation image and when acquiring an offset image, artifacts will occur in the radiation image after offset correction. This is because the occurrence of this artifact can be suppressed by making the number of binnings equal.

  In addition, the accumulation time at the time of acquiring the first offset image is made to match the accumulation time Ti1 at the time of acquiring the first image, and the accumulation time at the time of acquiring the second offset image is made to coincide with the accumulation time Ti2 at the time of acquiring the second image. Is preferred. By matching the accumulation time at the time of acquiring the radiation image with the accumulation time at the time of acquiring the corresponding offset image, more accurate offset correction can be performed.

  Further, it is preferable that the on-time of the TFT 8 in the read-out scanning cycle of the first offset image and the on-time of the TFT 8 in the read-out scanning cycle are equal to the on-time Ton1 of the TFT 8 in the readout scanning cycle of the first image, respectively. In addition, it is preferable that the on-time of the TFT 8 in the read-out scanning cycle of the second offset image and the on-time Ton2 of the TFT 8 in the read-out scanning cycle of the second image, respectively. Further, the reset scanning cycle at the time of reset before acquiring the offset image and the ON time of the TFT 8 in the reset scanning cycle may be matched with the reset scanning cycle at the time of reset before acquiring the radiation image and the ON time of the TFT 8 during the reset scanning cycle, respectively. preferable. As described above, by making the image acquisition condition of the offset image coincide with the image acquisition condition of the radiation image, more accurate offset correction can be performed.

In the present embodiment, the image acquisition condition of the first offset image matches the image acquisition condition of the first image, the image acquisition condition of the second offset image matches the image acquisition condition of the second image, and a series of The reset condition before acquiring the offset image will be described as an example in the case where a reset condition that matches the reset condition before acquiring the radiation image is set.
Further, in the present embodiment, the reading scan at the time of acquiring the second offset image is used instead of the reset scanning of the radiation detecting element 7 before the image acquisition at the time of acquiring the radiation image, and the read scanning at the time of resetting the radiation detecting element 7 is performed. The number of binnings, the reset scanning cycle, and the on-time of the TFT 8 in the reset scanning cycle are set to be the same as the number of binning (1 × 1), the read-out scanning cycle Tr2, and the on-time Ton2 of the TFT 8 at the time of acquiring the second image. However, the present invention is not limited to this.

  Note that the radiation irradiation condition and the image acquisition condition corresponding to the imaging menu are stored in the storage unit 59, and the console 58 reads out the radiation imaging condition and the image acquisition condition from the storage unit 59, and relays the readout condition by the communication unit 58c. The setting may be made by transmitting to the radiation generating device 55 or the radiation image capturing device 1 via the device 54.

When the setting of the image acquisition condition is completed in the radiation image capturing apparatus 1, the control unit 22 executes an image acquisition sequence. FIG. 8 is a diagram schematically illustrating an image acquisition sequence executed in the radiation image capturing apparatus 1 after an imaging start instruction.
As shown in FIG. 8, the control unit 22 of the radiation image capturing apparatus 1 first performs an offset image acquisition process.
In the offset image acquisition processing, first, the control unit 22 controls the scan driving unit 15 and the like to set a predetermined number of binnings at the time of resetting the radiation detection element 7 before image acquisition, a reset scan cycle, and a reset scan. Each radiation detection element 7 is reset by the ON time of the TFT 8 in the cycle (that is, the number of binning at the time of reset before acquiring a radiation image (1 × 1), the reset scanning cycle Tr2, and the ON time Ton2 of the TFT 8 in the reset scanning cycle). Do.

  Next, the control unit 22 shifts to a charge accumulation mode in which the scan driving unit 15 applies an off-voltage to all the scanning lines 5 to accumulate charges in the radiation detection element 7, and the radiation image capturing apparatus 1 , The dark charge is accumulated while waiting for a preset accumulation time in the first offset image (that is, the accumulation time Ti1 at the time of acquiring the first image) (first dark accumulation).

  Next, the control unit 22 shifts to the readout mode, controls the scan driving unit 15 and the readout circuit 17 and the like, and sets the binning number, the readout scan period, and the readout scan period at the time of the first offset image acquisition that are set in advance. The charge stored in each radiation detection element 7 is read out during the ON time of the TFT 8 (that is, the number of binning (2 × 1) at the time of acquiring the first image, the readout scanning period Tr1, and the ON time Ton1 of the TFT 8 in the readout scanning period). To obtain image data of the first offset image (first dark reading).

  Next, the control unit 22 shifts to the charge accumulation mode again, applies the off-voltage to all the scanning lines 5 by the scan driving unit 15, and sets the radiation image capturing apparatus 1 in a state in which the radiation image capturing apparatus 1 is not irradiated with radiation. The accumulation of the dark charges is performed while waiting for the accumulation time of the second offset image (that is, the accumulation time Ti2 at the time of acquiring the second image) (second dark accumulation).

Next, the control unit 22 shifts to the readout mode, controls the scan driving unit 15 and the readout circuit 17 and the like, and sets the binning number, the readout scan period, and the readout scan period at the time of the second offset image acquisition that are set in advance. The charge accumulated in each radiation detecting element 7 is read out during the ON time of the TFT 8 (that is, the number of binning (1 × 1) at the time of acquiring the second image, the readout scanning period Tr2, and the ON time Ton2 of the TFT 8 in the readout scanning period). To obtain image data of the second offset image (second dark reading).
Note that the second dark reading is simultaneously reset of the radiation image acquisition processing.

  The first offset image and the second offset image are obtained by the above-described offset image obtaining process. The control unit 22 repeatedly executes the offset image acquisition process until the notification signal of the pressing of the second switch of the exposure switch 56 from the radiation generation device 55 is received.

  When the photographing preparation is completed, the photographer presses the first switch of the exposure switch 56, and then presses the second switch. When the first switch is pressed, the exposure switch 56 transmits an activation signal to the radiation generator 55 via the console 57. Upon receiving the activation signal, the radiation generator 55 causes the radiation source 52 to be in a standby state by, for example, starting rotation of the anode of the X-ray tube of the radiation source 52.

  When the second switch is pressed, the exposure switch 56 transmits a radiation irradiation start signal to the radiation generator 55 via the console 57.

  Upon receiving the radiation irradiation start signal from the exposure switch 56, the radiation generator 55 transmits a second switch press notification signal to the radiation image capturing apparatus 1 via the relay 54. When the radiographic image capturing apparatus 1 receives the press notification signal of the second switch and is ready to complete the offset image acquisition process being executed or the like, the radiographic image capturing apparatus 1 sends an interlock release signal to the radiation generating apparatus 55 via the repeater 54. Send Upon receiving the interlock release signal transmitted from the radiation image capturing apparatus 1 via the repeater 54, the radiation generator 55 irradiates radiation from the X-ray tube of the radiation source 52 based on the radiation irradiation conditions.

  When the interlock release signal is transmitted, the control unit 22 shifts to the charge accumulation mode, applies the off-voltage to all the scanning lines 5 by the scanning driving unit 15, and sets the preset accumulation time Ti1 in the first image. Only after waiting, the charge generated in each radiation detection element 7 due to the irradiation of radiation is accumulated in each radiation detection element 7 (first accumulation).

  Next, the control unit 22 shifts to the readout mode, controls the scan drive unit 15 and the readout circuit 17 and the like, and sets a predetermined binning number (2 × 1) at the time of acquiring the first image, a readout scan period Tr1, In addition, the charge accumulated in each radiation detection element 7 is read out at the ON time Ton1 of the TFT 8 in the readout scanning cycle to acquire the image data of the first image (first main reading).

  Next, the control unit 22 shifts to the charge accumulation mode again, applies the off-voltage to all the scanning lines 5 by the scan driving unit 15, waits for the preset accumulation time Ti2 in the second image, The charge generated in each radiation detection element 7 due to the irradiation of radiation is accumulated in each radiation detection element 7 (second accumulation).

Next, the control unit 22 shifts to the readout mode, controls the scan driving unit 15 and the readout circuit 17 and the like, and sets a predetermined binning number (1 × 1) at the time of acquiring the second image, a readout scan period Tr2, In addition, the charge accumulated in each radiation detecting element 7 is read out at the ON time Ton2 of the TFT 8 in the readout scanning cycle, and the image data of the second image is obtained (second main reading).
The first image and the second image are acquired by the above-described reset before the image acquisition (second dark reading of the final offset image acquiring process) to the second main reading process (radiation image acquiring process). That is, the radiation image capturing apparatus 1 can perform the offset image acquisition processing and the radiation image acquisition processing by repeating the same driving.

  After the radiation image acquisition processing, the control unit 22 performs offset correction processing by subtracting the signal value of the corresponding pixel of the first offset image from the signal value of each pixel of the first image. Further, offset correction is performed by subtracting the signal value of the corresponding pixel of the second offset image from the signal value of each pixel of the second image. Here, in the offset correction process, the first offset image and the second offset image acquired in the offset image acquisition process immediately before the radiation image acquisition process may be used, or the first and second offset images acquired in the plurality of offset image acquisition processes may be used. The average value or the median value of each of the first offset image and the second offset image may be calculated and used as the first offset image and the second offset image. By calculating an average value or a median value of a plurality of offset images, offset noise can be reduced. In addition, when an offset difference occurs due to a difference in the acquisition time of the offset image, the acquisition time is weighted high for the new image, the low weight is applied to the old image, and then the average value is obtained. Noise reduction may be compatible.

  The control unit 22 performs a correction process such as a gain correction process, a defective pixel correction process, and a lag (afterimage) correction process on the first image and the second image, and processes the corrected first image and the second image. The image data is transmitted to the console 58 by the communication unit 39.

  When receiving the image data of the first image and the second image by the communication unit 58c, the control unit 58b of the console 58 performs enlargement interpolation processing on the first image or performs reduction interpolation (digital binning) processing on the second image. Thus, after matching the binning numbers of the first image and the second image, a difference image between the first image and the second image is generated, and the first image, the second image, and the difference image are used as patient information, imaging conditions, and the like. The information is stored in the storage unit 59 in association with the information or displayed on the display unit 58a. The difference image can be generated by, for example, multiplying a signal value of a pixel corresponding to each of the first image and the second image by a weight coefficient to obtain a difference.

As described above, when continuously capturing a plurality of radiation images (the first image and the second image) having different binning numbers, the radiation image capturing apparatus 1 performs the acquisition of the plurality of radiation images and the reset before the image acquisition. Then, a plurality of offset images corresponding to each radiation image are acquired by matching the binning number at the time of image acquisition with the binning number at the time of image acquisition, and offset correction processing is performed on each radiation image. Therefore, occurrence of an artifact due to offset correction in each radiation image can be suppressed.
Furthermore, by making the accumulation time at the time of acquisition of each of the plurality of offset images coincide with the accumulation time at the time of capturing the corresponding radiographic image, it is possible to perform more accurate offset correction.
Further, at least one of the following is set: at least one of the following: a reset scan cycle at the time of acquiring a plurality of radiation images, a reset scan cycle, an ON time of the TFT 8 in the reset scan cycle, a read scan cycle at the time of each image acquisition, and an ON time of the TFT 8 in the read scan cycle. By acquiring a plurality of offset images corresponding to each of the plurality of radiation images, it becomes possible to perform more accurate offset correction. Furthermore, the acquisition time of a plurality of radiation images and the reset scanning cycle, the on-time of the TFT 8 in the reset scanning cycle, the readout scanning cycle in acquiring each image, and the on-time of the TFT 8 in the readout scanning cycle are all made to coincide with each other. By acquiring a plurality of offset images corresponding to each, the effective accumulation time of each scanning line 5 at the time of acquiring each offset image (total accumulation time from completion of the final reset to accumulation of electric charges and start of reading). Can be made to substantially match the effective accumulation time at the time of acquiring the corresponding radiation image, so that more accurate offset correction can be performed.

  Also, in the DES mode, the first image can be read at high speed by setting the number of bins in the vertical direction at the time of acquiring the first image to be captured first to be greater than 1, so that the first image and the second image can be read. Can be shortened, and artifacts in a captured image due to body movement of a subject can be suppressed. Further, although the first image captured at a low tube voltage has poor granularity, the reading of the charge accumulated in the imaging by irradiating the subject with the low tube voltage (that is, the acquisition of the first image) is performed by the high tube voltage. By performing the reading with a larger number of bins than the reading of the charge accumulated in the imaging in which the subject is irradiated with the radiation with the voltage (that is, the acquisition of the second image), the noise of the first image can be reduced.

<Second embodiment>
Hereinafter, a second embodiment of the present invention will be described.
In the second embodiment, an example will be described in which in the DES mode, an offset image (a first offset image and a second offset image) corresponding to each image is acquired after the acquisition of the first image and the second image.

  Since the configuration of the second embodiment is the same as that described in the first embodiment, the description is referred to, and the operation of the second embodiment will be described below.

  First, the photographer performs photographing preparation. For example, a photographing menu (for example, a photographing mode (here, a DES mode), a photographing region, a photographing direction, and the like) is selected via the input unit 60 on the console 58, and a photographing start instruction is input. The photographer performs positioning of the subject, the radiation source 52, and the radiation image capturing apparatus 1.

In the console 58, when an imaging menu is set by the input unit 60 and an instruction to start imaging is input, the control unit 58b sends an instruction to start imaging in the selected imaging menu by the communication unit 58c to the radiation generating device 55 and the radiation source. The image is transmitted to the image photographing device 1.
Upon receiving the radiographing menu, the radiation generator 55 emits radiation (e.g., radiation (first radiation) for acquiring a first image) and radiation (second radiation) for acquiring a second image according to the radiation menu. (Irradiation), tube current, tube voltage, irradiation time, radiation irradiation interval between the first irradiation and the second irradiation, and the like.
Upon receiving the imaging menu, the control unit 22 of the radiation image capturing apparatus 1 sets a radiation image acquisition condition and an offset image acquisition condition according to the imaging menu. Examples of the radiation image acquisition condition and the offset image acquisition condition are the same as those described in the first embodiment, and thus the description will be referred to.

  In the present embodiment, the binning number of the first image is 2 × 1, the binning number of the second image is 1 × 1, the binning number of the reset is 2 × 1, the reset scan cycle before image acquisition is Tr0, and the reset scan cycle The case where the ON time of the TFT 8 is set to Ton0 will be described as an example. The other settings of the radiation image acquisition condition and the offset image acquisition condition are the same as those described in the first embodiment, and thus the description is referred to.

  Note that the radiation irradiation condition and the image acquisition condition corresponding to the imaging menu are stored in the storage unit 59, and the console 58 reads the radiation imaging condition and the image acquisition condition from the storage unit 59, and communicates the read condition. The information may be transmitted to the radiation generator 55 or the radiation image capturing apparatus 1 via the repeater 54 by the unit 58c and set.

  When the setting of the image acquisition condition is completed in the radiation image capturing apparatus 1, the control unit 22 executes an image acquisition sequence. FIG. 9 is a diagram schematically illustrating an image acquisition sequence executed in the radiographic image capturing apparatus 1 after an imaging start instruction in the second embodiment.

  As shown in FIG. 9, the control unit 22 of the radiation image capturing apparatus 1 first controls the scan driving unit 15 and the like to set a predetermined binning number at the time of resetting the radiation detection element 7 before image acquisition ( 2 × 1), each radiation detection element 7 is reset by the reset scanning cycle Tr0 and the ON time Ton0 of the TFT 8 in the reset scanning cycle. The control unit 22 repeatedly executes the reset until a notification signal of pressing the second switch of the exposure switch 56 from the radiation generation device 55 is received.

  When the photographing preparation is completed, the photographer presses the first switch of the exposure switch 56, and then presses the second switch. When the first switch is pressed, the exposure switch 56 transmits an activation signal to the radiation generator 55 via the console 57. Upon receiving the activation signal, the radiation generator 55 causes the radiation source 52 to be in a standby state by, for example, starting rotation of the anode of the X-ray tube of the radiation source 52.

  When the second switch is pressed, the exposure switch 56 transmits a radiation irradiation start signal to the radiation generator 55 via the console 57.

  Upon receiving the radiation irradiation start signal from the exposure switch 56, the radiation generator 55 transmits a second switch press notification signal to the radiation image capturing apparatus 1 via the relay 54. The radiation image capturing apparatus 1 transmits an interlock release signal to the radiation generating apparatus 55 via the repeater 54 when the notification of the pressing of the second switch is received and preparations such as completion of resetting are completed. Upon receiving the interlock release signal transmitted from the radiation image capturing apparatus 1 via the repeater 54, the radiation generator 55 irradiates radiation from the X-ray tube of the radiation source 52 based on the radiation irradiation conditions.

  When the interlock release signal is transmitted, the control unit 22 shifts to the charge accumulation mode, applies the off-voltage to all the scanning lines 5 by the scanning driving unit 15, and sets the preset accumulation time Ti1 in the first image. Only after waiting, the charge generated in each radiation detection element 7 due to the irradiation of radiation is accumulated in each radiation detection element 7 (first accumulation).

  Next, the control unit 22 shifts to the readout mode, controls the scan drive unit 15 and the readout circuit 17 and the like, and sets a predetermined binning number (2 × 1) at the time of acquiring the first image, a readout scan period Tr1, In addition, the charge accumulated in each radiation detection element 7 is read out at the ON time Ton1 of the TFT 8 in the readout scanning cycle to acquire the image data of the first image (first main reading).

  Next, the control unit 22 shifts to the charge accumulation mode again, applies the off-voltage to all the scanning lines 5 by the scan driving unit 15, waits for the preset accumulation time Ti2 in the second image, The charge generated in each radiation detection element 7 due to the irradiation of radiation is accumulated in each radiation detection element 7 (second accumulation).

Next, the control unit 22 shifts to the readout mode, controls the scan driving unit 15 and the readout circuit 17 and the like, and sets a predetermined binning number (1 × 1) at the time of acquiring the second image, a readout scan period Tr2, In addition, the charge accumulated in each radiation detecting element 7 is read out at the ON time Ton2 of the TFT 8 in the readout scanning cycle, and the image data of the second image is obtained (second main reading).
The first image and the second image are obtained by the above-described reset-to-second-readout process (radiation image obtaining process) before the image is obtained.

  Next, the control unit 22 controls the scanning driving unit 15 and the like to set a predetermined number of binnings when resetting the radiation detection element 7 before image acquisition, a reset scanning cycle, and an ON time of the TFT 8 in the reset scanning cycle. (That is, each radiation detection element 7 is reset by the number of binning (2 × 1) at the time of reset before radiation image acquisition, the reset scanning cycle Tr0, and the ON time Ton0 of the TFT 8 in the reset scanning cycle). Here, the same number of resets as the reset performed in the radiation image acquisition processing are repeated. Thereby, the stability of the image after the offset correction in the subsequent stage can be improved.

  Next, the control unit 22 shifts to a charge accumulation mode in which the scan driving unit 15 applies an off-voltage to all the scanning lines 5 to accumulate charges in the radiation detection element 7, and the radiation image capturing apparatus 1 , The dark charge is accumulated while waiting for a preset accumulation time in the first offset image (that is, the accumulation time Ti1 in the first image) (first dark accumulation).

  Next, the control unit 22 shifts to the readout mode, controls the scan driving unit 15 and the readout circuit 17 and the like, and sets the binning number, the readout scan period, and the readout scan period at the time of the first offset image acquisition that are set in advance. The charge stored in each radiation detection element 7 is read out during the ON time of the TFT 8 (that is, the number of binning (2 × 1) at the time of acquiring the first image, the readout scanning period Tr1, and the ON time Ton1 of the TFT 8 in the readout scanning period). To obtain image data of the first offset image (first dark reading).

  Next, the control unit 22 shifts to the charge accumulation mode again, and applies an off-voltage to all the scanning lines 5 by the scanning driving unit 15 so that the radiation image capturing apparatus 1 is not irradiated with radiation. The accumulation of the dark charges is performed while waiting for the accumulation time in the second offset image (that is, the accumulation time Ti2 in the second image) (second dark accumulation).

Next, the control unit 22 shifts to the readout mode, controls the scan driving unit 15 and the readout circuit 17 and the like, and sets the binning number, the readout scan period, and the readout scan period at the time of the second offset image acquisition that are set in advance. The charge accumulated in each radiation detecting element 7 is read out during the ON time of the TFT 8 (that is, the number of binning (1 × 1) at the time of acquiring the second image, the readout scanning period Tr2, and the ON time Ton2 of the TFT 8 in the readout scanning period). To obtain image data of the second offset image (second dark reading).
The first offset image and the second offset image are acquired by the above-described reset to second dark reading process (offset image acquisition process).

After the offset image acquisition processing, the control unit 22 performs lag (afterimage) correction.
Here, as shown in FIG. 10A, when the subject signal of the first image is G1, the second image is an image in which the lag G11 of the first image is added in addition to the subject signal G2. Further, a lag G21 of the second image occurs in the first offset image. Therefore, as shown in FIG. 10B, if the first offset image is directly subtracted from the first image and offset correction is performed, an image in which the lag G21 of the second image appears as a virtual image is obtained. Therefore, lag correction for removing this virtual image is performed.

  FIG. 11 shows the elapsed time t from the second image acquisition time and the magnification α of the lag generated in the offset image (how many times the lag remains in the second image when the reset is continued before the offset image acquisition). FIG. 6 is a graph showing a relationship with a value indicating whether or not there is an error. As shown in FIG. 11, when the reset is continued before the offset image is obtained, it can be seen that the lag generated in the offset image with the passage of time is attenuated. This decay curve was obtained by experiment. Therefore, the control unit 22 performs the lag correction of the first offset image by obtaining the magnification α.

The magnification α can be calculated by the following method.
First, an image G is created by matching the second image to the binning size of the first image. Here, an image G having a binning number of 2 × 1 is created by digitally binning the second image. Next, a magnification α at which the average value (or the median value) of the signal values of the image G and the average value (or the median value) of the signal values of the first offset image substantially match is calculated. For example, the magnification α can be calculated by dividing the average value of the signal values of the first offset image by the average value of the signal values of the image G.
Then, a lag of the first offset image can be removed by subtracting a value obtained by multiplying the signal value of the corresponding pixel of the image G by α from the signal value of each pixel of the first offset image.

  Note that the lags G11 and G21 may also exist in the second offset image, but even if the lags G11 and G21 remain in the second offset image, the lags G11 and G21 remain as virtual images in the second image after the offset correction processing. Since it does not appear, the lag correction may be omitted. However, lag correction may be performed on the second offset image. In this case, for example, the average value of the signal values of the second offset image is divided by the average value of the signal values of the second image to calculate the magnification β of the lag generated in the second offset image, and the respective values of the second offset image are calculated. By subtracting the value obtained by multiplying the signal value of the corresponding pixel of the second image by β from the signal value of the pixel, the lag of the second offset image can be removed.

  After the lag correction, the control unit 22 performs a correction process such as an offset correction process, a gain correction process, and a defective pixel correction process, and transmits the corrected image data of the first image and the second image to the console 58 by the communication unit 39. Let it. Since the offset correction processing is the same as that described in the first embodiment, the description is referred to.

  When receiving the image data of the first image and the second image by the communication unit 58c, the control unit 58b of the console 58 performs enlargement interpolation of the first image or reduction interpolation (digital binning) of the second image to thereby combine the first image with the first image. After adjusting the binning number of the second image, a difference image between the first image and the second image is generated, and the storage unit 59 associates the first image, the second image, and the difference image with patient information, imaging conditions, and the like. Or displayed on the display unit 58a.

As described above, in the second embodiment, as in the first embodiment, when a plurality of radiation images (first image and second image) having different binning numbers are continuously captured, a plurality of radiation images are acquired. A plurality of offset images corresponding to each radiation image are acquired by matching the binning number at the time of image acquisition and the reset before image acquisition and the binning number at the time of image acquisition, and perform an offset correction process on each radiation image. Therefore, occurrence of an artifact due to offset correction in each radiation image can be suppressed.
Furthermore, by making the accumulation time at the time of acquisition of each of the plurality of offset images coincide with the accumulation time at the time of capturing the corresponding radiographic image, it is possible to perform more accurate offset correction.
Further, at least one or more of a reset scan cycle at the time of acquiring a plurality of radiation images and before the image acquisition, an ON time of the TFT 8 in the reset scan cycle, a read scan cycle at the time of each image acquisition, and an ON time of the TFT 8 in the read scan cycle. By obtaining a plurality of offset images corresponding to each of the plurality of radiation images by matching the above, it is possible to perform more accurate offset correction. Furthermore, the reset scan cycle before and after the acquisition of a plurality of radiation images, the on-time of the TFT 8 in the reset scan cycle, the read scan cycle in each image acquisition, and the on-time of the TFT 8 in the read scan cycle are all made to coincide with each other. By acquiring a plurality of offset images corresponding to each of the radiation images, the effective accumulation time of each scanning line 5 at the time of acquiring each offset image (from the completion of the final reset to the start of accumulation and reading of the charge). Since the total accumulation time can be made to substantially match the effective accumulation time at the time of acquiring the corresponding radiation image, it is possible to perform more accurate offset correction.

  Also, in the DES mode, the first image can be read at high speed by setting the number of bins in the vertical direction at the time of acquiring the first image to be captured first to be greater than 1, so that the first image and the second image can be read. Can be shortened, and artifacts in a captured image due to body movement of a subject can be suppressed. Further, although the first image captured at a low tube voltage has poor granularity, the reading of the charge accumulated in the imaging by irradiating the subject with the low tube voltage (that is, the acquisition of the first image) is performed by the high tube voltage. By performing the reading with a larger number of bins than the reading of the charge accumulated in the imaging in which the subject is irradiated with the radiation with the voltage (that is, the acquisition of the second image), the noise of the first image can be reduced.

Although the embodiment of the present invention has been described above, the description in the above embodiment is a preferred example of the present invention, and the present invention is not limited to this.
For example, in the first and second embodiments, the first offset and the second offset are continuously performed before or after capturing the first image and the second image in response to one operation of the exposure switch 56. Although it has been described that the image is acquired, that is, the radiation image acquiring process and the offset image acquiring process are performed continuously, the offset image acquiring process is performed in advance to acquire the first offset image and the second offset image. After storing the first image and the second image in the storage unit 40, the first offset image and the second offset image may be read from the storage unit 40 and offset correction processing may be performed. Also in this case, the first offset image and the second offset image acquired in one offset image acquisition process may be stored in the storage unit 40, or may be acquired in a plurality of offset image acquisition processes. The average value or the median value of each of the first offset image and the second offset image may be calculated and stored in the storage unit 40 as the first offset image and the second offset image. By calculating an average value or a median value of a plurality of offset images, offset noise can be reduced. Also, a case where a plurality of offset images acquired by the plurality of offset image acquisition processes are stored in the storage unit 40 in association with the time and order of acquisition, and an offset difference occurs due to a difference in the acquisition time of the offset images. Alternatively, the average value may be obtained after giving a high weight to an image whose acquisition time is new and giving a low weight to an old image. This makes it possible to achieve both offset coincidence and offset noise reduction.

  Further, in the above-described embodiment, the radiographic image capturing apparatus 1 performs the offset correction process and then transmits the radiographic image capturing apparatus 1 to the console 58. The control unit 58b of the console 58 transmits the set of offset images to each of the plurality of radiation images using the offset images corresponding to each of the plurality of radiation images received from the radiation image capturing apparatus 1 by the communication unit 58c. An offset correction process may be performed. That is, the entire process from the acquisition of the radiographic image and the offset image to the offset correction process may be completed by the radiographic image capturing apparatus 1, or may be completed by a system including the radiographic image capturing apparatus 1 and the console 58. .

  In addition, the detailed configuration and detailed operation of each device constituting the radiation image capturing system can be appropriately changed without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Radiation imaging device 5 Scanning line 6 Signal line 7 Radiation detection element 8 TFT (switch means)
Reference Signs List 15 scanning drive means 15a power supply circuit 15b gate driver 17 readout circuit 22 control means 50 radiation image capturing system 55 radiation generation device 55a communication unit 57 console 58 console 58b control unit 58c communication unit 60 input unit r area P detection unit

Claims (5)

A plurality of radiation detecting elements arranged two-dimensionally,
An image acquisition circuit for acquiring and acquiring an image by causing the radiation detection element to accumulate and emit charges and reading out the emitted charges.
A radiographic imaging system comprising:
By controlling the image acquisition circuit, a radiation image acquisition unit that continuously acquires a plurality of radiation images by varying at least the number of binning,
By controlling the image acquisition circuit, the number of binning at the time of resetting the radiation detection element before image acquisition and the number of binning at the time of image acquisition coincide with those at the time of acquisition of the series of the plurality of radiation images, and Offset image acquisition means for acquiring the plurality of offset images corresponding to each of the radiation images,
Correction means for performing offset correction on the plurality of radiation images using the offset images corresponding to each of the plurality of radiation images,
A radiographic imaging system comprising:   The offset image acquiring unit may further match the charge accumulation time of the radiation detecting element with that at the time of acquisition of each of the series of the plurality of radiation images, so that the plurality of offsets corresponding to each of the plurality of radiation images are obtained. The radiographic imaging system according to claim 1, wherein the radiographic imaging system acquires an image. The image acquisition circuit includes a switch unit that emits electric charge from the radiation detection element when turned on.
The offset image acquisition unit may further include at least one of a reset scan cycle, an on-time of the switch unit in the reset scan cycle, a read scan cycle, and an on-time of the switch unit in the read scan cycle. The radiation image capturing system according to claim 1, wherein the plurality of offset images corresponding to each of the plurality of radiation images are acquired in accordance with a time when the plurality of radiation images are acquired. A radiation irradiation device that irradiates the radiation detection element with radiation at different tube voltages a plurality of times,
The radiation image capturing system according to any one of claims 1 to 3, wherein the radiation image acquiring unit acquires the plurality of radiation images using radiation irradiated at different tube voltages.   The radiation image acquisition unit controls the image acquisition circuit, and reads out the radiographing performed by the radiation irradiated at the low tube voltage among the radiations irradiated at the different tube voltages, using the radiation irradiated at the high tube voltage. 5. The radiographic image capturing system according to claim 4, wherein the number of binning operations is larger than the number of readouts in the image capturing.

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